Decode values from binary instead of text format

lib/Database/PostgreSQL/Opium/Error.hs

@@ -1,6 +1,7 @@
 module Database.PostgreSQL.Opium.Error (Error (..), ErrorPosition (..)) where
 
 import Control.Exception (Exception)
+import Data.ByteString (ByteString)
 import Data.Text (Text)
 import Database.PostgreSQL.LibPQ (ExecStatus, Oid, Row)
 
@@ -15,7 +16,7 @@ data Error
   | ErrorMissingColumn Text
   | ErrorInvalidOid Text Oid
   | ErrorUnexpectedNull ErrorPosition
-  | ErrorInvalidField ErrorPosition Oid Text String
+  | ErrorInvalidField ErrorPosition Oid ByteString String
   deriving (Eq, Show)
 
 instance Exception Error where

lib/Database/PostgreSQL/Opium/FromField.hs

@@ -7,42 +7,42 @@ module Database.PostgreSQL.Opium.FromField
   , fromField
   ) where
 
-import Data.Attoparsec.Text
-  ( Parser
-  , anyChar
-  , choice
-  , decimal
-  , double
-  , parseOnly
-  , signed
-  , string
-  , takeText
-  )
+import Data.Attoparsec.ByteString (Parser)
+import Data.Bits (Bits (..))
+import Data.ByteString (ByteString)
 import Data.Functor (($>))
 import Data.Proxy (Proxy (..))
 import Data.Text (Text)
+import Data.Word (Word32, Word64)
 import Database.PostgreSQL.LibPQ (Oid)
-import GHC.Float (double2Float)
+import Unsafe.Coerce (unsafeCoerce)
 
+import qualified Data.Attoparsec.ByteString as AP
+import qualified Data.ByteString as BS
 import qualified Data.Text as Text
+import qualified Data.Text.Encoding as Encoding
 
 import qualified Database.PostgreSQL.Opium.Oid as Oid
 
 (\/) :: (a -> Bool) -> (a -> Bool) -> a -> Bool
 p \/ q = \x -> p x || q x
 
-fromField :: FromField a => Text -> Either String a
+fromField :: FromField a => ByteString -> Either String a
 fromField =
-  parseOnly parseField
+  AP.parseOnly parseField
 
 class FromField a where
   validOid :: Proxy a -> Oid -> Bool
   parseField :: Parser a
 
+instance FromField ByteString where
+  validOid Proxy = Oid.bytea
+  parseField = AP.takeByteString
+
 -- | See https://www.postgresql.org/docs/current/datatype-character.html.
 instance FromField Text where
   validOid Proxy = Oid.text \/ Oid.character \/ Oid.characterVarying
-  parseField = takeText
+  parseField = Encoding.decodeUtf8 <$> AP.takeByteString
 
 -- | See https://www.postgresql.org/docs/current/datatype-character.html.
 instance FromField String where
@@ -53,45 +53,54 @@ instance FromField String where
 -- This instance accepts all character types but fails to decode fields that are not exactly one character.
 instance FromField Char where
   validOid Proxy = validOid @Text Proxy
-  parseField = anyChar
+  parseField = do
+    str <- parseField
+    case str of
+      [c] -> pure c
+      _ -> fail "Char accepts single characters only"
+
+intParser :: (Bits a, Num a) => Parser a
+intParser = readBigEndian <$> AP.takeByteString
+  where
+    readBigEndian = BS.foldl' (\x b -> x `shiftL` 8 .|. fromIntegral b) 0
 
 -- | See https://www.postgresql.org/docs/current/datatype-numeric.html.
 -- We assume that 'Int' has 64 bits. This is not guaranteed but reasonable enough.
 instance FromField Int where
   validOid Proxy = Oid.smallint \/ Oid.integer \/ Oid.bigint
-  parseField = signed decimal
+  parseField = intParser
 
 -- | See https://www.postgresql.org/docs/current/datatype-numeric.html.
 instance FromField Integer where
   validOid Proxy = Oid.smallint \/ Oid.integer \/ Oid.bigint
-  parseField = signed decimal
+  parseField = intParser
 
 instance FromField Word where
   validOid Proxy = Oid.smallint \/ Oid.integer \/ Oid.bigint
-  parseField = decimal
-
-doubleParser :: Parser Double
-doubleParser = choice
-  [ string "NaN" $> nan
-  , signed (string "Infinity" $> infinity)
-  , double
-  ]
-  where
-    nan = 0 / 0
-    infinity = 1 / 0
+  parseField = intParser
 
+-- | See https://www.postgresql.org/docs/current/datatype-numeric.html.
+-- Accepts only @real@ fields, not @double precision@.
 instance FromField Float where
   validOid Proxy = Oid.real
-  parseField = fmap double2Float doubleParser
+  -- Afaict there's no cleaner (@base@) way to access the underlying bits.
+  -- In C we'd do
+  --
+  -- union { float a; uint32_t b; } x;
+  -- x.b = ...;
+  -- return x.a;
+  parseField = unsafeCoerce <$> intParser @Word32
 
+-- | See https://www.postgresql.org/docs/current/datatype-numeric.html.
+-- Accepts only @double precision@ fields, not @real@.
 instance FromField Double where
-  validOid Proxy = Oid.real \/ Oid.doublePrecision
-  parseField = doubleParser
+  validOid Proxy = Oid.doublePrecision
+  parseField = unsafeCoerce <$> intParser @Word64
 
 boolParser :: Parser Bool
-boolParser = choice
-  [ string "t" $> True
-  , string "f" $> False
+boolParser = AP.choice
+  [ AP.word8 1 $> True
+  , AP.word8 0 $> False
   ]
 
 -- | See https://www.postgresql.org/docs/current/datatype-boolean.html.

lib/Database/PostgreSQL/Opium/Oid.hs

@@ -5,6 +5,11 @@ import Database.PostgreSQL.LibPQ (Oid (..))
 eq :: Eq a => a -> a -> Bool
 eq = (==)
 
+-- raw byte string
+
+bytea :: Oid -> Bool
+bytea = eq $ Oid 17
+
 -- string types
 
 text :: Oid -> Bool